Goals of the work are: (1) To understand the action of pyridoxal phosphate (PLP) and other coenzymes in enzymatic catalysis. (2) To develop new spectrophotometric methods of wide application in biochemistry and molecular biology. (3) To prepare new analogs of PLP and to test them with purified apoenzymes and in model systems. This year we intend to: (1) Complete our analysis of absorption spectra of aldehydes and Schiff bases. (2) Conduct nmr studies on a number of 3-hydroxypyridines. We hope to use information about chemical shifts in various positions in the pyridine ring together with existing data on microscopic dissociation constants and shifts in electronic spectra to provide a detailed understanding of the way in which electron density within the ring varies with a state of protonation at the ring nitrogen and phenolic sites. (3) To continue the synthesis of analogs of pyridoxal sulfate including the sulfonic acids. (4) To continue our study of the reactions of pyridoxal sulfate and 4'-ethynyl PLP with apoAAT.